Hey Dean,
I'm a little late to this party but here's my two cents worth - I would upgrade each of my sets of Klipschorns with a Klipsch-engineered, tested and measured top end for a two-way system. One of the things that attracted me to Klipsch many years ago was the low - obsolescence product design philosophy and (particularly for the Klipschorn) a stated commitment to improvements in detail allowing the owner to keep them up-to-date for a lifetime. I fully understand and appreciate that there is a legacy in the stability of the design but one could argue just as strongly that there is also a legacy in the countless improvements that have been introduced over many decades for this speaker.
Let me add some perspective: I first heard Klipschorns at my bosses' house when I was 17 and was in awe. I bought that same pair when I was 18, living in a college dorm. I didn't buy my first car until I was 20 - just goes to show how important great speakers are. The first time I met PWK, I had owed them for about a year. They were an unmatched pair (1950's vintage) with different versions of the K-5 midrange horns and different crossovers and woofers in each cabinet. He explained in detail the various changes that had been made and some of the engineering tradoffs that were faced along the way. When I asked what updates should be done to my pair he surprised me by suggesting certain specific, but not all possible updates. Needless to say, I was greatly impressed by the man's character. Now 30+ years later I still greatly enjoy all my heritage speakers (21 and counting) - yeah I know, Coulter is still winning! []
I came away from that meeting with two very clear perspectives: Paul was very intolerant of casual or misinformed criticism of the performance of his company's products, yet he was philosophical about the fact that no current product, design or technology represented anything like perfection. It was clear from his comments at the time that ongoing research and development directed toward product improvement should and would take place.
Dean, you have the benefit of hearing the Jubilees now as well as modern vs. modded klipschorns in your recent past. These are experiences I haven't had yet. My order for Jubilees will be placed next week. You are in a great position to compare and contrast the results of a range of different approaches. From the comments I have heard about large-format two-way systems, I think there would be considerable interest in a properly engineered, tested and measured system that is a factory- supported update. That approach would seem to be consistent with the longtime philosophy of Klipsch and provide the type of long -term product support that built the reputation and loyal following Klipsch enjoys today.
Dean, thanks for a great thread.
Bill W.